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Flat Response question

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Flat Response question

Postby Bwoodwardmusic » Sat Jan 11, 2014 11:53 pm

Hey guys!

I understand this might sound like a bit of a silly question; but I can't find an answer to it anywhere.

I am basically wondering why monitors and headphones cannot (or don't choose to be) made with a totally flat response. Surely if having a totally flat and "uncoloured" sound is the most accurate to mix on, then why not make gear with it? (as opposed to having all this (3db) variation etc.)

Cheers,

Ben
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Re: Flat Response question

Postby Exalted Wombat » Sun Jan 12, 2014 12:15 am

Good idea! May we see your designs? :-)
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Re: Flat Response question

Postby Bwoodwardmusic » Sun Jan 12, 2014 12:31 am

Here it is, just a rough design:

Response
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20hz .......................................................................30Khz
Frequency
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Re: Flat Response question

Postby dmills » Sun Jan 12, 2014 12:36 am

Because real components, and especially real transducers do not work like that!

Even on axis loudspeakers have various resonances and other weirdnesses that happen when you use a coil in a magnetic field to shake a paper cone in order to create noise, this gets worse when you add several in a box to cover the required range and the crossovers can only somewhat compensate (Also these effects tend to vary somewhat unit to unit due to materials and assembly tolerances).

Now consider the box itself, it has acoustic diffraction at the corners, is usually ported in an attempt to get more bass out of a too small box, so there are various effects from that, and now note that all of this changes in complicated ways as you move off axis....

Trust me the problem is not at all simple, and +-3dB is actually doing rather well, and is certainly better then most rooms are (The room is the other half of the acoustic system and is seldom given the attention it deserves)!

This question is equivalent to asking why can they (whoever 'they' are) not make a laptop battery that runs it for a year without recharging (Actually I can think of a way, but it would be rather 'hot')?

Regards, Dan.
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Re: Flat Response question

Postby Exalted Wombat » Sun Jan 12, 2014 3:33 am

Bwoodwardmusic wrote:Here it is, just a rough design:

Response
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|_________________________________________
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|_________________________________________
20hz .......................................................................30Khz
Frequency

Excellent! Is that a mic or a speaker? When will a prototype be ready?
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Re: Flat Response question

Postby turbodave » Sun Jan 12, 2014 10:44 am

It looks like a Mexican riding a bike! Dave :?
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Re: Flat Response question

Postby Zukan » Sun Jan 12, 2014 11:14 am

Dude's asked a perfectly valid question.

Guys, you're my bredren, treat our newcomers with some respect please.
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Re: Flat Response question

Postby Brian M Rose » Sun Jan 12, 2014 11:59 am

There are always going to be compromises, especially with any mechanical device. Although I've had nothing to do with speaker design, I have worked in the past with the team who developed a new very high quality periscope lens for film and TV use.
We wanted to produce something with the highest possible quality, which would match the best prime lenses available at the time. No easy call!
There is an inevitable compromise between size, optical performance, yeald and of course, cost. Computers have made life far easier, but with some 36 separate optical components, all that have to be specially ground and in some cases, calling for specific glass melts, with mechanical construction calling fore an accuracy of a few microns, it takes time, effort and sweat. It was NOT a cheap lens (about £48,000.00) but did its job, superbly.
I suspect that high quality monitor speakers are no different. It's not just a case of quality, but more important, consistency. In other words, the same type of speaker, in different studios will deliver exactly the same performance.; this is quality control.
Coming back to out lens, we had to reject about 75% of the delivered optical components as they were delivered - I have since discovered that this is par for the course for other lenses of this quality.
So, in the end, it is far easier to design a produce a speaker that will sound 'flattering' than one that will reveal the signal as accurately as possible. The compromise lies in just how far you can go, and still make a product that is financially viable for both manufacturer and end user.
A similar thing has occurred elsewhere on this forum. Many people are non professionals who want to take advantage of the huge range of equipment that is now available. Much of this equipment returns remarkably high audio quality, but may not be as reliable as (for example) equipment designed for the broadcast industry, which tends to be mission critical. For the latter, expect to pay several times as much for such features as double-redundant power supplies and long term reliability. In the end, actually sound all that different.
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Re: Flat Response question

Postby Persian Bit » Sun Jan 12, 2014 12:40 pm

Hi Ben,
Good question, and it applies to other electronic-acoustic equipments as well. Why they can't produce a microphone that can capture the whole frequency spectrum just flat as you tried to show? The same goes with pre-amps and compressors, mixing consoles,etc. Every brand of these gears have their own character and color, while trying to offer us a flat and transparent sound.

Because in theory and on paper [and even in SOS posts!] you can design something that is perfectly ok, but when it comes to building it in real world with real matterials, the whole game begins. A lot of different factors begin to affect your design like physic, chemistry and acoustics and it's very hard to control and balance all these fighting components to make a truely flat system. At least with our current technology it's still impossible, but with the rise of digital technology we're getting closer and closer.

In case of your question, an speaker is not only an electronic piece of work. The cones, the electronic parts, wirings, the box itself [which is very important] and many other little things are acting together to produce what you hear. And usually none of these parts are 100% perfect [neither in design nor in production]. Even with those little fundamental electronic pieces that are used to build the electronic board [resistors, capacitors,etc], they varry in quality and output. You can't find two tubes that work exactly like each other , and i believe that's the beauty of analog...

To keep it short, all these systems are not 'Linear' [where you expect them to work the same in all situations] and the system components react and sound different depending on how you push them. Even you build that perfect flat system in your lab, it will work totally different in real world with different humidity, air pressure and temprature values.

That's why the most flat gears are usually expensive cause a lot of time,research and production costs have been put to create them.

However, we still need to have the most flat mics and speakers in our studios to produce the right output, but I believe in today's world the 'Flat' term doesn't make sense anymore since people's ears are heavily damaged with colored processed sound of commercial records, radio and TV. A true flat mix will sound boring and naked to most of people whom have been listening to musics with harsh hi mids and heavy sub sonics [Except jazz and classical music recordings].

So while you try to maintain that flatness, don't bother too much thinking about it.
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Re: Flat Response question

Postby dmills » Sun Jan 12, 2014 12:41 pm

That sounds about right, transducers are really the place where (far more then the electronics) it is all about engineering compromise.

Frequency response, phase response, box size, linearity, cost, yield, efficiency, reliability, sensitivity, off axis lobing, it all trades off in complicated ways and trying too hard to optimize one parameter will inevitably make the others go down the pan.

Further I would argue that on axis response is actually not something worth a great deal of effort to optimize, as the room will have a huge effect and can be driven as much by off axis energy as on, and the actual frequency response of the system (room and speaker) tends to be something that the engineer becomes used to in short order, phase response and linearity are (provided the frequency response is reasonable) probably at least as important and are seldom even specified.

Reasonable people can of course disagree about the way to make these tradeoffs and that is why there is more then one brand of monitors out there....

Regards, Dan.
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Re: Flat Response question

Postby Hugh Robjohns » Sun Jan 12, 2014 2:13 pm

Bwoodwardmusic wrote:I am basically wondering why monitors and headphones cannot (or don't choose to be) made with a totally flat response.


Most decent monitors are designed to be as flat on-axis as it is practical to make them, given the size and cost of the monitor in question. The story is often different with 'hi-fi' monitors which might be 'voiced' to sound a little more flattering and less analytical, by shaping the response slightly.

This is the response of the Neumann KH310, which is flat to better (much better, in fact) than +/-2dB between 36Hz and 20kHz:

Image

You won't find anything significantly better than that, and many won't be as good.... but this on-axis response is only a very tiny part of the speaker's overall technical performance. You'll see a lot of the relevant (but still not exhaustive) performance measurements of this specific monitor illustrated HERE And bear in mind that these plots all exclude the normal interactions and effects of placing the speaker in a room...

However, as others have highlighted, electro-mechanical transducers are inherently full of compromises due to the physics and practical construction requirements involved. One of the most significant aspects is the way the frequency response changes as the listener moves off-axis -- again all tied up with the physics of the driver and cabinet sizes, and the crossover arrangements.

That inherently non-flat (or 'coloured') sound is directed into the 300 degrees of the room outside the normal listening area, to bounce off of the various surfaces which all have different reflective capabilities at different frequencies too. As Dan said, the room acoustics form at least half of the overall sound character and quality, even if most people don't do anything about it!

The bottom line is that speaker designers do generally to get the on-axis response as close to a flat line as possible through the majority of the audio band, but the real world gets in the way and is far more intrusive in electro-mechanical devices like speaker and microphone transducers than it is in the world of electronics.

H
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Re: Flat Response question

Postby Slash7 » Sun Jan 12, 2014 6:50 pm

I think in headphones Audeze is the closest one to ideal response.But they're goddamned expensive. Just see the graph:

Image
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Re: Flat Response question

Postby turbodave » Sun Jan 12, 2014 6:50 pm

Zukan wrote:Dude's asked a perfectly valid question.

Guys, you're my bredren, treat our newcomers with some respect please.
Sorry Zuke...Felt it was OK as Mr. Mills had answered so well. :blush:
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Re: Flat Response question

Postby John Willett » Mon Jan 13, 2014 10:11 am

This thread appears to be broken - the right side of all the replies is missing as asr all the top-right buttons including "quote" etc...

Needs looking at.
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Re: Flat Response question

Postby Zukan » Mon Jan 13, 2014 10:31 am

Thanks John. I'll get that seen to.

Dave, no issues pal. Always a decent bloke you be..
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Re: Flat Response question

Postby Hugh Robjohns » Mon Jan 13, 2014 10:41 am

John Willett wrote:This thread appears to be broken - the right side of all the replies is missing as asr all the top-right buttons including "quote" etc...

This is one of the bugs of our old forum software, where it appears to fail to correctly resize some image formats correctly. However, the problem manifests mainly in Windows Explorer, and if you view the forum in an alternative browser -- such as Chrome -- the pages format completely correctly!

Anyway... I've fixed it now.

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Re: Flat Response question

Postby Pete Kaine » Mon Jan 13, 2014 10:59 am

Slash7 wrote:I think in headphones Audeze is the closest one to ideal response.But they're goddamned expensive. Just see the graph:

Image

Once you hear the LCD3's however... Let's just say, you don't listen to them unless you've a lottery win in your back pocket.
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Re: Flat Response question

Postby Bwoodwardmusic » Mon Jan 13, 2014 8:59 pm

Thanks for all the replies guys! They were all very informative and helpful!
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Re: Flat Response question

Postby John Willett » Tue Jan 14, 2014 11:12 am

Hugh Robjohns wrote:
John Willett wrote:This thread appears to be broken - the right side of all the replies is missing as asr all the top-right buttons including "quote" etc...

This is one of the bugs of our old forum software, where it appears to fail to correctly resize some image formats correctly. However, the problem manifests mainly in Windows Explorer, and if you view the forum in an alternative browser -- such as Chrome -- the pages format completely correctly!

Anyway... I've fixed it now.

H

Thanks - actually I was viewing it via Firefox on a Mac.
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Re: Flat Response question

Postby John Willett » Tue Jan 14, 2014 11:16 am

Slash7 wrote:I think in headphones Audeze is the closest one to ideal response.But they're goddamned expensive. Just see the graph:

Image


Headphones are listened to sitting on the head and many headphones have a tailored response to take account of this - the idea is that they have a flat response, as much as possible, at your ear.

I am always very wary of HeadRoom's frequency curves as they would be measured differently from the manufacturer.

HOWEVER - they are a good tool to compare headphones as all the HeadRoom graphs would me measured the same way - just don't take them as gospel.
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Re: Flat Response question

Postby Exalted Wombat » Tue Jan 14, 2014 2:46 pm

John Willett wrote:Headphones are listened to sitting on the head and many headphones have a tailored response to take account of this - the idea is that they have a flat response, as much as possible, at your ear.

Note, however, the dramatic difference that often results from positioning the headphone cups slightly differently on your ears. Particularly from pressing them a little tighter in.
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